   protocols/IRegionReader
   (read-in-region [this region]
     (protocols/read-in-region this region {}))
-  (read-in-region [this {:keys [chr start end]} {:keys [depth] :as option}]
+  (read-in-region [this {:keys [chr start end]} option]
     (logging/warn "May cause degradation of performance.")
     (filter
      (fn [v] (and (if chr (= (:chr v) chr) true)

  [^java.io.BufferedReader rdr header kws]
  (when-let [line (.readLine rdr)]
    (if-not (or (meta-line? line) (header-line? line))
      (cons (parse-data-line line header kws)
            (lazy-seq (read-data-lines rdr header kws)))
      (read-data-lines rdr header kws))))


;; ------------------

(defn- parse-data-line
  [line kws]
  ;; When splitting a string with single-character delimiter,
  ;; `java.lang.String#split` is slightly faster than `clojure.string/split`.
  ;; For more details, please refer to https://github.com/chrovis/cljam/pull/29.
